Quiet propeller

ABSTRACT

Provided is a quiet propeller including a propeller blade having such a pitch angle not at its root portion but at its blade end edge portion with respect to a relative flow in the rotational direction, as to raise the internal pressure of a liquid thereby to eliminate a cavity, a water bubble or a cavitation at the blade root portion at the time of a high-speed rotation so that the propeller is rotated at a high speed by a small prime mover and by a prime mover capable of moving much fluid backward. In the quiet propeller, a propeller blade is curved backward at its leading end portion to form a slope portion, and a rotational front side end portion in the slope portion is formed into an arcuate shape in the side view whereas a rotational rear side end portion is so gradually extended backward from the rotational front side end portion as to become straight from the blade root to the blade end, thereby to form a deflecting slope face. At the rotating time, the fluid is pushed toward the back axis from the deflecting slope face in the slope portion.

TECHNICAL FIELD

The present invention relates to a quiet propeller, and in particular toa quiet propeller comprising a plurality of propeller blades, the bladehaving a pitch angle to increase pressure into the center of thepropeller during high speed rotation not to produce voids, bubbles orcavitation, thereby allowing high-speed rotation with a small motor andpushing back a lot of fluid.

BACKGROUND OF THE INVENTION

In a conventional screw propeller for underwater thrust, a blade istilted with respect to a main shaft at the part close to the center ofthe propeller and the blade twists from the center to the periphery.

JP8-72794A discloses a high-speed thrust machine in which a blade tiltsrearward.

In a conventional screw propeller for ships, a pitch angle is large atparts close to the center of the propeller, so that the propeller isthick and water flow twists with rotation of the propeller.

When rotational speed increases, water flow does not circulate along thepitch angle. Fluid leaves the blade surface to produce cavitation tocause noises and bubbles.

Twisting of water flow and cavitation cause loss in rotational energy.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a quiet propeller inwhich central part of the propeller is not twisted, a pitch angle beingformed at a peripheral part of the blade to increase internal pressure,rotating faster without cavitation or noise, the propeller being usablefor an air-conditioning fan, a ventilating fan, a pump and a windmill.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rear elevational view of the first embodiment of a quietpropeller according to the present invention.

FIG. 2 is a top plan view thereof.

FIG. 3 is a rear elevational view of the second embodiment of a quietpropeller according to the present invention.

FIG. 4 is a top plan view thereof.

FIG. 5 is a rear elevational view of the third embodiment of a quietpropeller according to the present invention.

FIG. 6 is a top plan view thereof.

FIG. 7 is a rear elevational view of the fourth embodiment of a quietpropeller according to the present invention.

FIG. 8 is a top plan view thereof.

FIG. 9 is a rear elevational view of the fifth embodiment of a quietpropeller according to the present invention.

FIG. 10 is a top plan view thereof.

FIG. 11 is a front elevational view of the sixth embodiment of a quietpropeller according to the present invention.

FIG. 12 is a front elevational view of the seventh embodiment of a quietpropeller according to the present invention.

FIG. 13 is a rear elevational view of the eighth embodiment of a quietpropeller according to the present invention.

FIG. 14 is a side view thereof.

FIG. 15 is a side view of a propeller blade.

FIG. 16 is a side view of a propeller blade.

FIG. 17 is a side view of a propeller blade.

FIG. 18 is a side view of a propeller blade.

FIG. 19 is a sectional view taken along the line A-A in FIG. 13.

FIG. 20 is a sectional view taken along the line B-B in FIG. 13.

FIG. 21 is a sectional view taken along the line C-C in FIG. 13.

FIG. 22 is a side view of a quiet propeller used as a screw propeller.

FIG. 23 is a rear elevational view of the ninth embodiment.

FIG. 24 is a side view of the quiet propeller in FIG. 13.

FIG. 25 is a side view of a boat including a propeller according to thepresent invention.

FIG. 26 is a front view of a flying boat including a propeller accordingto the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

Embodiments of the invention will be described. FIG. 1 is a rearelevational view of a quiet propeller according to the presentinvention, and FIG. 2 is a top plan view. The propeller 1 comprises fourpropeller blades 2 equally spaced around a boss 1 a. The number of thepropeller blades 2 is not limited to four.

The propeller blades 2 are substantially equal to each other in lengthfrom the base to the end. Between a first side edge 2 c and a secondside edge 2 d, there is a bent line 2 a.

From the bent line 2 a, a tilted end portion 2 b which tapers is formed.

The tilted end portion 2 b is tilted from the belt line 2 a.

An angle of the tilted end portion 2 b is variable from 15 to 45 degreesdepending on the length of the blade 2 b.

In FIG. 2, the tilted end portion 2 b is 15% of the blade length, butmay range 15-60%.

In FIG. 1, from the end of the first side edge 2 c of the blade 2 to thesecond side edge 2 d, a diagonal line 2 e extends.

From the diagonal line 2 e, a tilted back surface 2 f rises toward thesecond side edge 2 d having a pitch angle. The diagonal line 2 e in FIG.1 is straight, but may be curved.

In FIG. 2 in which the propeller blade 2 is seen horizontally, the firstside edge 2 d becomes thinner gradually from the center to the distalend of the blade 2.

In the tilted back surface 2 f, a pitch angle P ranges from 7 to 25degrees.

There is no pitch angle on the rear surface of the blade 2 close to thecenter of the propeller 1. The surface tilts up from the diagonal line 2e to form the tilted back surface 2 f at the pitch angle P with respectto a rotational direction.

If required, the pitch angle P at the part close to the boss 1 a may be0 to four degrees.

To propel a ship, when the propeller 1 turns clockwise in FIG. 1, waterflow is prohibited by the tilted end 2 b from diffusing centrifugally,but pushed rearward by the tilted end portion 2 b and the tilted backsurface 2 f.

In a conventional screw propeller, there is a greater pitch angle closeto the boss of the blade 2. So water flows along the surface of a pitchangle at low speed rotation. But water leaves the surface at high speedrotation to produce voids which causes decrease in internal pressure tomake bubbles and noises. The propeller 1 in this invention does notcause such phenomena.

With rotation of the propeller 1, the blade 2 at the boss 1 a does nothave a pitch angle with respect to turning flow. Thus, at high speedrotation, fluid is pushed toward the center, so that internal pressureincreases. Cavitation for producing voids, vortexes and bubbles are notproduced to keep quiet rotation without noise.

The pitch angle P of the peripheral end of the blade reduces waterresistance during rotation, increasing rotational speed of the propeller1. High speed rotation increases rotational speed of the periphery ofthe blade 2 to push more water to increase a thrust. In this invention,the blades 2 have nearly equal and narrow width. There is no pitch angleclose to the boss of the propeller and the pitch angle P is gentlecloser to the periphery of the propeller 1.

The shape of the propeller 1 causes neither vortex nor cavitation. Theblade 2 is narrow and a pitch angle at the periphery is gentle therebyreducing resistance during rotation to enable high speed rotation. Thetilted end 2 b prevents water flow from diffusing to gather water flowtoward the center of the back surface to realize efficient thrust.

The propeller can be used as a blowing fan for an air conditioner or aventilator. A small motor enables the propeller to turn at high speedwithout noise.

Embodiment 2

FIG. 3 is a rear elevational view of the second embodiment of apropeller according to the present invention, and FIG. 4 is a top planview thereof.

In the second embodiment, a bent line 2 a of a propeller blade 2 is setto be positioned at 40% of a radius of the propeller 1 from theperipheral end. A tilted end portion 2 b has a length of 40% of that ofthe blade 2 or radius of the propeller. But it is not limited thereto.

A tilted back surface 2 f and the tilted portion 2 b having a pitchangle P are broader than those in the first embodiment to enable waterpushing amount to increase. The length of the tilted end portion 2 b isset to be 15-60% of the length of the blade 2. If the tilted end portion2 b is longer, a tilting angle of the tilted end portion 2 b may besmaller.

Embodiment 3

FIG. 5 is a rear elevational view of the third embodiment of a propellerand FIG. 6 is a top plan view. The same numerals are allotted to thesame members as those in the former embodiments, and description thereofis omitted.

In the third embodiment in FIG. 5, the distal end of a second side edge2 d of a propeller blade 2 contacts a bent line 2 a. A diagonal line 2 eextends from the connecting point to the proximal end of a first sideedge 2 c.

In FIG. 6, the first side edge 2 c becomes thinner from the boss 1 a tothe periphery of the propeller 1. With respect to the diagonal line 2 e,a propeller blade 2 tilts forward to form a pitch angle P. In FIG. 6,the pitch angle P ranges from 7 to 25 degrees.

In the third embodiment, a pitch angle is not formed close to the centerof the propeller 1. Thus, during high speed rotation, there is neithervoid nor vortex. So bubbles, noise or cavitation does not occur.

At the boss 1 a of the propeller 1, part behind the diagonal line 2 e isbroader, providing high rigidity. So the blade can be made thinner toallow resistance to decrease during rotation.

With rotation of the blade 2, the blade 2 pushes back water close to thebent line 2 a using a tilted back surface 2 f of the pitch angle P, sothat its reaction thrusts a ship.

During rotation, water does not diffuse centrifugally of the blade 2,but is pushed back to allow the ship to go forward by the reaction.

At the same time, with water flowing through the blades 2, the blade 2turns naturally, thereby reducing driving force of a motor. This isbecause the blade 2 turns by force coming to the front of the blade 2 aswell as a propeller blade which rotates by wind.

In a conventional screw propeller, water twists and goes rearward of thescrew propeller. So force for twisting water is excessive and causesloss in power. Water which flows from front does not smoothly go throughtwisted water which goes rearward, resulting in bubbles and cavitation.

In contrast, the propeller blade 2 according to the present inventionhas no pitch angle close to the boss of the propeller. So water whichdoes not twist reduces water resistance during the rotation of the blade2. Flowing back of water with a gentle pitch angle close to theperiphery is unlikely to twist, but provides more smooth flow to enablenoise and bubbles to decrease with less power loss.

The propeller 1 according to the present invention rotates faster thanconventional screw propellers. A motor with less driving power can beused.

With the maximum length bent line 2 a, the pitch angles P of the tiltedback surface 2 f and tilted end portion 2 b improve fluid-transferringefficiency.

At the same time, water which flows along the front surface of the blade2 to the rear surface flows rearward with negative pressure on the frontsurface of the blade 2. Water on the rear surface of the blade 2 ispressed by the tilted back surface 2 f repeatedly.

Water which flows through the blade 2 smoothly and strongly speeds upthe rotation of the propeller 2.

The propeller 1 which is small in size but produces a higher thrust issuitable for ships. It is also used as a steering wheel for ships.

By changing its radius, the blade 2 may be employed as a fan for an airconditioner and a ventilator.

The propeller 1 produces a thrust by water or wind which flows acrossthe blades. For blowing wind, the blade 2 may be made thinner withoutnoise with greater blowing amount.

A motor for driving the propeller can be made smaller and the propellercan be used widely as a fan of an air conditioner, a ventilating fan ina tunnel or pump.

FIG. 7 is a rear elevational view of the fourth embodiment of apropeller according to the present invention, and FIG. 8 is a top planview thereof. The same numerals are allotted to the same members anddescription thereof is omitted.

In the fourth embodiment, a first side edge 2 c of a propeller blade 2is provided with respect to a second side edge 2 d at a greater angletherebetween.

So a tilted back surface 2 f has a greater area. In FIG. 8, a pitchangle of the tilted back surface 2 f with respect to oncoming flow isgentle such as 15 degrees since the surface 2 f is longer along aturning direction of the blade 2.

A bent line 2 a is like an arc, and a tilted end portion 2 b is gentlytilted from the bent line 2. The tilted end portion 2 b has a pitchangle with respect to oncoming flow since the side edge highly tilts.

Thus, when the propeller 1 rotates, the surface with the pitch angle ofthe tilted back surface 2 f and tilted end portion 2 b pushes waterflow. The area with the pitch angle is away from the propeller shaft 4to make its thrust greater.

FIG. 9 is a rear elevational view of the fifth embodiment of a propelleraccording to the present invention. FIG. 10 is a top plan view thereof.The same numerals are allotted to the same members and descriptionthereof is omitted.

A tip of a blade in the fifth embodiment is narrower than that in thefourth embodiment. The blade is thinner and relatively flat therebyspeeding up the rotation compared with the former embodiments.

FIG. 11 is a front elevational view of the sixth embodiment according tothe present invention. In this embodiment, the rear surface in FIG. 1 isdeemed as front view. The left side of a diagonal line 2 e tiltsdownward and the propeller is used as a windmill.

A tilted front surface 2 g is formed between a diagonal line 2 e and asecond side edge 2 d, and has a pitch angle. Wind is received by thetilted front surface 2 g of the blade 2, so that the blade 2 rotates.

The flat part close to a boss of a propeller 1 is wider, but winddiffuses centrifugally with rotation, so that load is not given torotation.

Wind flow which diffuses centrifugally of the blade 2 is prohibited by atilted end portion 2 b and gathered into the tilted front surface 2 gwith the pitch angle thereby increasing pressure and rotational force ofthe propeller 1.

The tilted front surface 2 g is tilted rearward at the second side edge2 d. Oncoming wind flows along the tilted front surface 2 g and becomeshigh speed, lower air density or lower pressure than surrounding therebygathering onto the tilted front surface and improving rotational force.

With the rotation, wind which flows along a bent line 2 a rearwardpushes the blade 2. The bent line 2 a is close to the periphery of thepropeller 1 providing high torque. Rotational resistance and noise arelow. So the propeller is suitable for a wind mill for generatingelectric power and a waterwheel.

Embodiment 7

FIG. 12 is a front elevational view of the seventh embodiment of apropeller according to the present invention. The same numerals areallotted to the same members, and description thereof is omitted. Theembodiment 7 has a front elevational view corresponding to the rearsurface of FIG. 3. A tilted front surface 2 g is tilted between adiagonal line 2 e and a first side edge 2 c such that the first sideedge 2 c projects forward, and the propeller is used as windmill.

Oncoming wind is received by the tilted front surface 2 g with a pitchangle and a blade 2 rotates clockwise as shown by an arrow in FIG. 12.

A flat part is wider close to the boss 1 of the propeller 1, but withrotation, wind flowing onto the part diffuses centrifugally. So it doesnot resist the rotation.

With the rotation, wind which diffuses centrifugally of the blade 2 isprohibited by a tilted end portion 2 b and gathered into a tilt frontsurface 2 g having a pitch angle thereby increasing rotational force ofthe propeller 1.

The tilted front surface 2 g is tilted such that the first side edge 2 cprojects forward from the diagonal line 2 e. Oncoming wind increases airdensity over the tilted front surface 2 g to push the blade 2 clockwise.

With the rotation of the blade 2, air goes toward the distal end of thediagonal line 2 e to push the blade 2 clockwise. The bent line 2 a isaway from the center of the propeller 1 to provide high torque. Lowrotational resistance causes low noise and the blade is suitable as awindmill for a wind power generator and a waterwheel.

This invention is not limited to the embodiments and variable dependingon its use. The bent line 2 a and the diagonal line 2 e need not be acorner, but may be a gentle slope. The circumferential part of the blade2 may be wider than the central part.

FIG. 13 is a rear elevational view of the eighth embodiment of afluid-collecting propeller and FIG. 14 is a side view.

In a small propeller 1, a plurality of blades 3 extends from a boss 1 aat regular intervals around a propeller shaft 4.

The propeller 1 is integrally molded with the boss 1 a and the blade 3.If required, the boss 1 a and blade 3 may be separately molded andjoined together.

The propeller 1 may be made of metal or by plastic molding. In plasticmolding, the shaft 2 is made of metal and the blade 3 is made ofplastics. They are combined together.

In FIG. 13, S denotes a basic radial line. At the boss 1 a, a distancebetween a first side edge 3 a and the basic radial line S is equal tothat between the basic radial line S and a second side edge 3 b.

At the periphery of the blade 3, a distance between the second side edge3 b and the basic radial line S is much wider than that between theradial line S and the first side edge 3 a to form broader surface 3 c.

The maximum chord length of the flowing surface is set to about 50% of aradius of the propeller 1, but is not limited thereto. The total area ofthe rear surface of the blade 3 may preferably be less than a half ofthe area of a circle with the radius of rotation of the blade 2.

In FIG. 14, the first side edge 3 a of the blade 3 extends along thefront end line F by a half of the radius from the center of thepropeller 1, and the remaining of the first side edge 3 a is a curvedportion 3 d.

In FIG. 14, an axis L is at right angles to the front end line F. An endline T is in parallel with the axis X, and the distance P-O is equal tothe radius O-Q.

The distance V-Q is a depth of the propeller 1. The distance U-Q isequal to the distance V-Q. A diagonal line W between P and Q crosses aline passing through V in parallel with the front end line F at a pointR and also crosses a line passing through U. The curved portion 3 d isan arc of a circle around the point R. Depending on the rotationalradius of the blade 3 or depth of the blade 3, the curved portion 3 d isvariable in size. If the distance P-O is longer than the distance O-Q,the arc surface of the curved portion 3 d varies. The arc may be part ofan ellipse.

The curved portion 3 d prevents fluid from diffusing during rotation.The arc of the curved portion 3 d may be part of a circle or ellipse,but an arc line G of 10% may be an angle close to the end line T.

For example, in FIG. 15, the distance Q-G is 10% of the distance O-Q orrotational radius. The 10% arc line G is tilted at about 22 degrees withrespect to the end line T. The end of the curved portion 3 d is nearlyin parallel with the end line T, so that fluid which flows centrifugallyis prohibited by the curved portion 3 d and directly to the center ofthe propeller 1.

In FIG. 16, the depth of a curved portion 3 d is smaller. In FIGS. 17and 18, the distance Q-U is larger than the distance V-Q. When thecurved portion 3 d is part of a circle, an angle of the arc line G withrespect to the end line T can be made smaller.

FIG. 19 is a sectional view taken along the line A-A in FIG. 13;

FIG. 20 is a sectional view taken along the line B-B: and FIG. 21 is asectional view taken along the line C-C.

As shown in FIG. 21, the bottom of the first side edge 3 a lowers bythickness, while the bottom of the second side edge 3 b is curveddownward.

In FIG. 19, the first side edge 3 a extends along the front end line F.The rear end edge 3 a is away from the line F and the tilted surface 3 eis formed.

The tilted surface 3 e changes a direction of fluid and is tilted at30-50 degrees with respect to the axis L.

Therefore, when the propeller 1 rotates right in FIG. 13, fluid whichcomes across the first side edge 3 a is directed into the center of thepropeller 1 by the tilted surface 3 e in FIG. 19.

FIG. 22 is a side view in which the propeller 1 is used as a screwpropeller 5 a for a motorboat. The numeral 5 b denotes a motorboat, 5 cdenotes an engine, and 5 d denotes a handle. When the propeller 1rotates, water flows centripetally. Conventionally, water diffusescentrifugally. But in this invention, the curved portion 3 d is formednear the periphery and water is surrounded by the curved portion 3 d andflows centripetally.

Water passing across the first side edge 3 a is directed by the tiltedsurface 3 e centripetally, strongly pushed out through behind thepropeller 1 and gathered like a cone.

The closer water gets to the vertex of the cone, the higher waterpressure becomes. So a stronger thrust can be produced than awater-diffusing propeller. A lower displacement of the engine canrealize a smaller size to allow the engine to provide higherperformance.

The propeller does not produce noise for stirring water because watersurrounded by the tilted portion 3 d is pushed out through like a cone.In a conventional screw propeller, water which diffuses centrifugallycollides with water which flows back. The propeller 1 is suitable in usefor a submarine requiring soft sounds.

Even if the propeller blade 3 is above the water in half, rpm will rise,so that the motorboat will run faster. A conventional screw propeller isaffected by air, but the propeller of this invention is not affected.

Embodiment 9

FIG. 23 is a rear elevational view of the ninth embodiment of apropeller according to the present invention, and FIG. 24 is a sideview. The same numerals are allotted to the same elements, anddescription thereof is omitted.

In the ninth embodiment, four propeller blades 3 are provided. Threeblades are more efficient than four blades according to tests as a screwpropeller because of water resistance. But with an engine torque, fourblades will be preferable.

In the ninth embodiment, a tilted surface 3 e is set to be longerhorizontally. So stronger flow comes centripetally. A tilted portion 3 dis narrower than that in FIG. 13 to allow the tilted surface 2 e tobecome gentler.

In FIG. 25, the propeller 1 in the ninth embodiment 1 is employed as anair thrust machine. The numeral 5 denotes a boat; 6 denotes anunderwater blade; 7 denotes a lifting blade; and 8 denotes a rudder.

When the propeller 1 rotates, wind does not diffuse, but is stronglypushed back like a cone as straight airflow to achieve higher thrust inFIG. 24.

The rudder 8 for the boat 5 in FIG. 25 is amphibious. Wind which ispushed out of the propeller 1 is concentrated, thereby providingexcellent control in the rudder 8.

When the boat 5 runs, the boat 5 rises to the surface with theunderwater blade 6 and the lifting blade 7. Water resistance under theboat becomes smaller to speed up the boat. The higher engine for thepropeller 1 can fly above the water.

FIG. 26 is a front elevational view where the propeller 1 is employedfor a flying boat. A small engine enables sliding over the water, andhigher torque engine enables flying through the air. The propeller 1 isused for leisure, marine farm transportation and island interconnection.

This invention is not limited to the foregoing embodiments, but variabledepending on its use.

The propeller does not diffuse fluid, but gathers it centripetally. Itis used as a screw propeller and an air thrust machine.

1. A quiet propeller driven by a motor, comprising: a boss at a centerof the propeller; and a plurality of blades extending from the boss,each of said plurality of blades having a first side edge and a secondside edge, a line F extending along the blade perpendicular to an axisof the propeller, a first pitch angle of the blade close to the bosswith respect to the line F being defined from 0 to four degrees, thefirst side edge being gradually thinner from the boss to a distal end ofthe blade, a tilted portion rising centrifugally at a rear surfacetoward the distal end of the blade from a bent line connecting a distalend of the first side edge to a distal end of the second side edge, atilted back surface rising toward the second side edge between the firstside edge and the second side edge, a second pitch angle of the secondside edge to the line F ranging from 7 to 25 degrees, whereby fluid fromthe first side edge is gathered centripetally of the propeller by thetilted portion and the tilted back surface during rotation of thepropeller.
 2. The quiet propeller of claim 1 wherein the first pitchangle of the blade is
 0. 3. A quiet propeller driven by a motor,comprising: a boss at a center of the propeller; and a plurality ofblades extending from the boss, each of said plurality of blades havinga first side edge and a second side edge, a line F extending along theblade perpendicular to an axis of the propeller, a first pitch angle ofthe blade close to the boss with respect to the line F being definedfrom 0 to four degrees, the first side edge being gradually thinner fromthe boss to a distal end of the blade, a tilted portion risingcentrifugally at a rear surface toward the distal end of the blade froma bent line connecting a distal end of the first side edge to a distalend of the second side edge, a diagonal line being defined from anintersection of the first side edge with the bent line to the secondside edge, a tilted back surface rising from the diagonal line to thesecond side edge, a second pitch angle of the second side edge to theline F ranging from 7 to 25 degrees whereby fluid from the first sideedge is gathered centripetally of the propeller by the tilted portionand the tilted back surface during rotation of the propeller.
 4. Thequiet propeller of claim 3 wherein the first pitch angle of the blade is0.
 5. A quiet propeller driven by a motor, comprising: a boss at acenter of the propeller; and a plurality of blades extending from theboss, each of said plurality of blades having a first side edge and asecond side edge, a line F extending along the blade perpendicular to anaxis of the propeller, a first pitch angle of the blade close to theboss with respect to the line F being defined from 0 to four degrees,the first side edge being gradually thinner from the boss to a distalend of the blade, a tilted portion rising centrifugally at a rearsurface toward the distal end of the blade from a bent line connecting adistal end of the first side edge to a distal end of the second sideedge, a diagonal line being defined from an intersection of the secondside edge with the bent line to the second side edge, a tilted backsurface rising from the diagonal line to the first side edge, a secondpitch angle of the second side edge to the line F ranging from 7 to 25degrees, whereby fluid from the first side edge is gatheredcentripetally of the propeller by the tilted portion and the tilted backsurface during rotation of the propeller.
 6. The quiet propeller ofclaim 5 wherein the first pitch angle of the blade is 0.